Process of purification of sugar solutions



June 1, 1937.

J. S. REICHERT ET AL RAM SUGAR HYDROGEN PEROXIDE v 5? IRAL CRUS H ERMAkJH TANK SPIRAL PHHGLER SWEET WATER STALL! HE FORM WATER CEHTRFUGE' DAMP C RE EH wAsHE-D AFHNATION X Q 'Q SUGAR SYRUP r B t M E LT OF MlLKOFLIME 60 BRIX ZEE 51.0w UP TANKS 5TEAM LONG DRAG;

TAHK5 v v MlLKOF LlME L FE QQQ comlfigsslin B v LOW UP TAH K3 STEAM 7 L1CLEAR LIGHT UQUOR FIRST HYDROGEN PEROXDE Bmx Fi l' i SWEETLAHD F\ LT ER5y I M MULTIPLE EFFECT EVAPORATORS CLE AR FlRsT L Que? CLOUDY F \LTRATEI'PEROXIDE mcnon Vessa' CLEAR DARK uauorz T 60 BRlX C H .INVENTOR5:23E512? JOsEPH s- 'REICHEE'T,

& 124mm 13. ELUQTT, TREATMENT TO RECOVER m CQ$HE suqAR ATTORNEY PatentedJune 1, 1937 t 2,082,850 a rnoorzss or PURIFICATION onls uelm i 7somrrrons Joseph s. Reichert and Ralph Emmott. Niagara Falls,

N.--Y., assiznors 'Nemours & Company, Wilmington; Del., a coriporationot Delaware i s L to E. L'du Pont de Application July 11, 1935, SerialNelson's! .9 Claims. (01. 127-64); I 7

air and steam and subjected to the action ff the pHftends to go up, thesolution be- I a This application relates to the decolorization andclarification of sugar containing liquors and syrups. More particularly,it relates to a'process for preparing a decolorized, granulated canesugar from raw sugars such as those of domestic f origin, or fromforeign sources as Cuba, Hawaii,

Puerto Rico and the Philippines. f

In the manufacture or .whitefgranulated cane sugar it is usual toutilize as the starting product raw sugar which i's obtained byevaporating to t dryness the juice. of the sugar cane. raw

product, which. will hereinafterbe termed rawfl sugar, ,is frequentlyimported" from various sources of supply outside of the .United States.

s11 11 as Cuba, Puerto Rico, Hawaii and the Philip-- 1 Usually it isshipped in large burlap bags, and inaddition to the dark color resultingfrom,

the sugar juice'itself it contains other dark colored] pines.

impurities.

[Ordinarily inthe course of therefining opera-. tion. the raw sugar issubjected toa number of treatments, 1 and. sugar-containing liquors nsyups are progressively subjected to, a number of v H M h ca f clusion ofthese steps the sugar liquoris ordinari y clarifying and decoloriz'ingsteps evaporated under reduced pressure untilwhat is termed in theindustry a"fmassecuiteffresultsr.

This is customarily doneiin vacuumlpans, and the granulated whiteproduct is recovered in this manner. ,In presentda'y operationssubstantially allot the decolorizing lis faccomplishedfl by subjecting,the sugar syrups or liguors to the action a of an alkali such, as milkof lime andlto the action of an, adsorbent decolorizl'ng' medium such asThesau u a il uo in era r r dissolving the raw sugar ina suitable:agueous,

3s cne ar oi. a v d a bo tice is first to treat the-sugar-ii medium in aprocess which will. separate it irf 'to dcry wlsan s a S u s i var u der esof: coloration. Each of these. p oducts ;is then subsequentlytreated to recovera refined product i by subjection tol the action-- ofan. alkali: such as milk of lime and to the action ofan adsorbentecolorizing 1 carbon, thereby removing a such as =15 large -por ;tionof. the-objectionable coloring -mat a :a desh m u t es In practiceit isessential. thatthe ugar-tom, taining solution beingv treated in order toremove, the dark colored discoloring materials should; be

50 substantially neutralin reaction. in commercial refining it isusualtomake a distinct effortto;

maintain the pH of the solution somewhere within the range-6.8 to 8.0. IOrdinarily in. the blow- 41 501 9? 12 e n 5W dl -w h th 55 sugarsolution is agitated by means of compressed:

coining somewhat alkalinein reaction. j During this step in ordinarycommercial practice the pH of thesug'ar solution may ,fall within therange 5 7.0 to'I9.0. I-Iowe'ver, for reasons which will now beexplained, it is essential that the solution shall j not varysubstantially from thecondition'of neutrality. Thus thepI-I should fallordinarily'vfvithin the range 6.8 to 7.5 and in noevent should fall 10outside the range 6.0 to 9.0. plicationthis latter pH range spokenfoi asone of substantialjneutrality. .1

In the treatment of solutions containing sucrose, which. is the'principalhsugar' in the cane 15 sugar of jcommercegthere is f dangerthat inver sion may "occur; .By inversion? is meantthe hydrolysis jofadisaccharide' sugar such assucrose" into a mo'nosaccharid'e. Thus, canesugar is "con vertedv by, inversion dextrose and levulo Z 20 Since theprocess isa hydrolysis reaction it is' atalyzed bydiluteacids andalkaliesandfpytheacgij tion of enzymes. The action \ofhydrogen ionsincatalyzing. invjersiorl is much more pronounced} than the action ofhydroxyl ions. Accordingly 25 if' inversionis to be prevented or reducedto asg'. large an extent as practicableha vpI-LbeloW 7. 0 j is much moreobjectionable than one abcye mo, As a matter offact, the pH of the sugarsolut on may go as high as 9.0 with little; or no inversionjj 30Although the conversion dismiss orf jcane ever, the chiefobjection toa'largeamouiitof in ver't sugar isthat it prevents crystallization:aThat 7 part of the sugar which is presentas invertsugar cannot becrystallizedtandx therefore represents a' substantial loss: in :thegranulated .s'sucrose yield: I The :xuncrystallized syrupy: 1 solutionremaining; which contains the invertpsugar, can onlyibe soldas i efi e ss ru i a r u b n in a. much lower-price on the market than granulatedcane. sugar.

I -the isalwaysdesirable'to prevent; on;

the vformation of invert sugar; to as great an extent as possible or mhe. lan uaee ottn industry; to keep down the percentage of inverts? Bcause of the efiect of hydrogen and hydroxyl ions in catalyzinginversion it is desirable that the pH of the sugar solution beingtreated be kept as close to 7.0, corresponding to exact neutrality. as 5is practicable. Ordinarily since the pH'tends to drop during the latterstages of the process, it is necessary during the blowup or liming stepthat the pH be brought up to 8.5 to 9.0. In any event the industry hasfound that whenever the pH value oi the sugar solution being treatedfalls outside of the range 6.0 to 9.0 inversion occurs to such an extentas to result in a product of diminished value. An essentialcharacteristic of our improved process therefore is that it involvesoperation under conditions wherein the sugar solution is maintainedsubstantially neutral in reaction.

.As stated, in present day commercial sugar refining operations, thediscoloring impurities are removed ordinarily by the action of an alkalisuch as milk of lime and by the action of an adsorbent such as bone charor activated carbon. In practice the sugar is treated with the milk oflime in a blow up tank wherein the temperature is elevated to one ofabout 185 F. and the solution agitated by means of compressed air andlive steam. Heating coagulates some of the impurities and the mainfunction of the lime is to regulate the pH of the sugar solution so thatit does not fall outside the range 6.0 to 9.0. The alkali also functionsto some extent to precipitate some of the constituents present in thesugar solution, particularly compounds of metal such as magnesium andiron. These precipitates are subsequently removed by filtration inSweetland filter presses and the clear liquid is then treated with bonechar or activated carbon, usually by filtering it again through bonechar filters.

Ordinarily in present commercial practice the 0 larger part of the coloris removed in the char filters. These filters are used up after a numberof hours of continuous service and must be replaced from time to time bynew filters or must have their active material replaced or revivified.In commercial refineries which handle large amounts of raw sugar intwenty-four hour operation there are usually a large number of thesecharcoal filters and the replenishment of the active material in them isa substantial part of the cost of refining. Any process which wouldlengthen the life of the charcoal filters by removing some of thediscoloring compounds and thus putting a lighter load on these filters,would be a distinct contribution to the industry. The process disclosedin this application utilizes an additional decolorizing and clarifyingagent. This agent is introduced into the usual and customary process ofcommercial refining. One of the essentials for the successful use of ournew decolorizing agent, hydrogen peroxide, is that the sugar solutionwhich is treated with the solution of hydrogen-peroxide utilized -besubstantially neutral in reaction (pH 6.0 to 9.0). This agent isordinarily used in addition to the color removing materials now largelyused, milk of lime and the bone char filters. It has been found that theuse of hydrogen peroxide under the conditions characteristic of ourimproved clarification and decolorizing process, greatly prolongs thelife of the bone char filters employed in commercial operation since thesugar solution in our process is ordinarily from 30 to decolorizedbefore it reaches these filters. Not only 75 is there no tendency in ourprocess for the perv in the refiner's syrup obtained at the conclusionof the refining process, high ash content is a decided disadvantage. Thehigher the ash content the lower the recovery of crystallized sucrose,and this is an added reason for a lowered ash content.

Hydrogen peroxide is now sold in large volume in aqueous solutions ofrelatively high concentration. The usual commercial strength is volumehydrogen peroxide solution, which means that one volume of this solutionwill yield approximately 100 volumes of oxygen gas when the solution isat 20 C. and the evolved gas is measured at 0 C. and 760 mm. of mercurypressure. Such a solution contains about 27.6% by weight of hydrogenperoxide. Solutions of 100 volume peroxide, such as those soldcommercially under the trade-marks Albone C and Perone, prepared by anelectrolytic process, are thesolutions that we prefer to use in ourprocess. The amounts subsequently specified are based on thesecommercial 100 volume solutions of hydrogen peroxide containingapproximately 27.6% by weight of hydrogen peroxide. However, solutionsof other strengths are frequently available, solutions of as high asvolume hydrogen peroxide having already been offered for sale. The usualdilute solutions sold in commerce are of lower volume concentrations,the 10, 17 and 25 volume solutions being usual. These solutions may alsobe used in our process but the amounts given below for 100 volumesolutions should be proportioned in accordance with the volumeconcentration of the hydrogen peroxide solution employed. Thus, when the25 volume concentration solution is used, the amount of the solutionemployed should be four times that which would be used were 100 volumeused. The same considerations apply for solutions of lower and higherconcentrations.

Solutions of hydrogen peroxide have already been suggested for use inthe clarification of sugar juices but the method disclosed fordecolorizing these products in the prior art have not been successful.Thus, suggestions for the use of oxygen evolving materials in theclarification of sugar juices go back as far at least as about 1860.Hydrogen peroxide has been variously suggested as the oxygen-evolvingcompound. In view of the fact that the literature contains references tothe use of hydrogen peroxide in decolorizing sugar juices and syrupsprior to 1900 it is significant that until the development" of theprocess described in this application there was never any commercial usemade of hydrogen peroxide for this purpose. The methods of the prior arthave been generally unsatisfactory and hydrogen peroxide as adecolorizing agent had been dismissed by sugar chemists as a substanceof very questionable and inferior utility in re, spect to its clarifyingand decolorizing properties. The lack of use of this age .1tcommercially is due to defects inherent in the prior art methods and theinfirmities in these methods rendering them commercially valueless willbe apparent from a comparison with the improved method forming thesubject matter of this application.

Prior methods suggested for the use of oxygen and efli'cientpurification subsequently' by the ac' 1 llzed'hydro'gen' peroxideinone'of the-two follow avat r 3 evolving compounds generally andhydrogen perhave also found that oxide specifically n; the decolorlzingor sugar syrups have gen rally "been restrictedto use'in theclarification of sugar derived irom beetsi Generally the'me thodsorth'eprior art h'ave'uti -T ing action and far ing manners,eltherimconjunction with a cata have therefore employed lytic materialtoSet'fiee the oxygn i'apldlyfsllcfi asbone 'char. "charcoal orme eigurmor in con f junction with 7 anacid treatment to destroythecoloringmatters which are said to beordinarlly gen 'peroxide basic in character.in processes of the secondthe greater portion of aboutwlfi minutes.classthe real function or the hydrogen peroxide dis'coveries, aftercareful investigation of the enis topredispose the liquor beihgj treatedto ready one phase of our-process; and in another, hydrouse of'hydrogenperoxide in tion of acids and acidic substances. t

Accordingly we have developed a process *in whichsubstantl'ally all ofth'e'hydrogen-peroxide is decomposed by thetime the solution frea'ches:the bone char or activated charcoal'iilters. We have found that it isnot possible to-dispenseem tirely with the step of treating'the sugarliquors with bone char or' 'activated carbon,= operating with hydrogenperoxide alone, since many of the" discoloring compounds can be 1removed" much I moreefiiciently and cheaply by theadsorbentjaction ofbone char than bythe action of hydrogen peroxide. Moreover; manydiscoloring substances probably are-removable onlybytre'ating the sugarsolution with :an adsorbenti However, in our process in order that thehydrogen peroxide may be econom'ically utilizedandthatrmaximum'clarifying and decoloring results ma'y be obtained for'the amount of hydrogenperoxide employed, we

" sugar,

find'that prolonged periods of contact between catalytic .bodies such asbe..xcarefully avoided. In

disclosed in. theliterature. At the same; time since our process isintended "for use in conjuncsigned to operate at thetime period usualand customary in commere cialmethods;

aeteristicsj of. our process as fol1ows:-.- v1. The rapid liberation ofoxygen the sugar solution and the hydrogen peroxide and the'ab'sence ofadded agents, whether they be bonechar or other rnaterials. fortherapid.,1iberation of oxygen, ar e lto this important respect f ourprocess differs completely from those already tionlwith a commercialrefiningmethod it isv dethe temperature and within "We maysummarizethe-three important char 7 from the crating in accordancecreased almost so operate that substantiallyall of the hydrogen hydrogenperoxide leaving lirom" 10 ito to be removed by theiadsorbentmaterial... Since theioadwon the bone char filters thus ,very muchreduced we have: found that the life of these filters in a with'our'method is .in-

.over sthe life of filters in plants. where the entire clarification andtdecolor' izing load is borne by=thzbone char;' -In"one"spe1- cifici'nstance we have found that the lifeof one-- typical filt'euwasextended from"50,000 to 90,000

- gallons,:the figure in each case representing athe number. of"gallons. 10f sugar containing liquor; passed through the :rfilter?beforethe bone. char need be replaced or revivifiedwa' llthoughzwhile.30 to 90% of the. discoloring ingredentst are destroyedibefore the?solution reachesathe bone" char 'ifilter when hydrogen peroxideis=:emp1oyed,. operating in accordancewith our .process; the remaining10 to90% comprises thosecolored materials which are best removed in an,economical.

- and etficient way byr-the' action;of anadsorbent:

suchrasbone char. 1-. 12; a It is important tobear in mind that thevprior.v

art. thought rapid liberation. of: oxygen: from yhy-J drogen peroxide.essential for satisfactory clariwi ficat-ion. An elevatedtemperaturefwas also cone:

sidered necessary, ,:the theory being that hydr0.-'

gen peroxide. being less. stable vat elevat ed temper-j? atures wouldthen decomposeimorerapidly. Sureprisingly enough,- after considerableexperimena tation; we have. found thatyan elevated .temperaw ture is notdesirable or; necessary iand that ax cessivetemperaturesrshould, ingeneral, be avoid? edx except as necessitated by. other process stepsutilized in the. complete refining; method. We

lution of hydrogen peroxide utilized is avoided and as longa periodofcontact between the hydrogen peroxide and .thesugarliquor as .is .pos-.sible in conjunction withthe particular refining process isuto beobtained. --Added agents,for the, rapid evolution of oxygen are not usedandare to be avoided; p 2. The; process is substantially neutral 7 1yindicated this means that I tion' should. not;vary appreciably,from 7.0and o e Carriedoutunder con- I cli-tionsdn; which the sugar solutionbeing treated" in reaction. TEAS previous the of the so1u-.

tir'eproblerhof decolorlzing sugar syrups bythe.

the refining of. raw indicate that the prior artwas completely inerrorwhen it regarded rapid liberation of oxy gen as critical ordesirable. Onthe contrary, we 5 should preierably fall withinthe range6.0 130.9 0.

This is, anse ssentialandevery. necessary partfof torsatisfactory: decolorizing and the, hydrogen peroxide and for keeping down thepercentage oi invert sugars resulting. Whenever fsubstantialneutralityor; substantially neutral? is 're ferr'e'dto this apg I our roc s otclarifying with.

plication a-pH.of 6.0t0 9.0 is intended. a

3. Our processis hydrogen peroxide and. an ad sorbehti materialtogether, in .the clarification such as. bonechar ea e ..us ail 91 m yav s e in W prior methodsnemployedf drogen peroxide. While I hydrogenperoxide inconjunction with. various d po n s m' tha l fic i n ces weemployhydrogen 5 perox de. without agents tend ingto {facilitate itsdecomposition and; as a. sepa e t eatmsm. s m

char, 1 or 3 some other commercially ,vali'iable form of ldecolorizingcarbon.

V distinguished from-those oi the prior art .in that it em my i beingtaken, however; to, insure substantially complete decomposition of thehy drogenv peroxide before the bone char filter an ad or ent uc as b ncharacteristics .of our novel and improyed method for explain in detail1 n explanation we will ireferv to the flow sheet annexed to thespecification. This flow sheet illustrates part of a.commerciai processnow widely employed in the refining of raw sugars. In describing ourmethod it must 5 be understood that it is not limited to operation inaccordance with the precise procedure indicated diagrammatically on theflow sheet but is generally useful in all processes of sugar refining,it being understood, of course, that all such processes will becharacterized by the three essential characteristics above discussed.

Taking the process illustrated on the flow sheet as illustrative, a rawcane sugar such as that obtained from domestic, Cuban, Puerto Rican,

Philippine or Hawaiian sources is first crushed in a spiral crusher. Thecrushed raw cane sugar is then permitted to flow into a spiral minglerwhere a thick slurry or magma is prepared by thoroughly mixing the sugarwith a liquid. As the liquid, "maish syrup is commonly employed,

which maish syrup is obtained in the continuous process as willsubsequently be apparent. As is evident from the flow sheet the maishtank is connected with the spiral mingler.

To the maish tank a solution of hydrogen peroxide is added at intervalsin amounts which will be subsequently specified. The flow sheet showsthe hpdrogen peroxide addition and it is evident that hydrogen peroxidefinds its way into the magma from the maish tank. If desired, the

' hydrogen peroxide solution may be added at any other point so that itfinds its way into the maish tank as, for instance, to the aifinationsyrup obtained from the centrifuge.

'35' In practice the magma may be prepared by mixing 100 pounds of theraw sugar with about 45 pounds of saturated maish syrup. During theprocess the maish tank may be maintained at a relatively elevatedtemperature, such as one in 40 the neighborhood of 150 F., so that theslurry in the mingler is at a temperature of about 110 F. At thiselevated temperature the viscosity of the magma is reduced to such anextent that it is readily flowable.

The magma is then permitted to fiow into the centrifuge. During thecourse of the operation, following the first centrifuging, the sides ofthe centrifuge are washed down with sweet water. Sweet water is asolution obtained by washing the bone char taken from bone char filterswhich have become exhausted in use, prior to revivification orreplacement of the active char.

During the centrifuging a relatively dark sugar liquor comes off firstand is collected in the receptacle marked Green affinition syrup. Afterremoval of the green aflination syrup thecentrifuge ordinarily isbrought into communication with a second receptacle for the wash syrup,

which is a relatively lighter colored liquor. Fi-

0 nally the solid product remaining in the centrifuge, damp washedsugar, is discharged into a separate vehicle.

As shown, about one-seventh of the green afiination syrup is permittedto flow through the line A to the blow up tanks. The remainingsixsevenths travels through the line B and is intermingled with the washsyrup and returned to the maish tank. This constitutes the maish liquor.Based on the sucrosepresent in the usual 70 raw sugar being treated,ordinarily about 92% of the solid matter will be found in the dampwashed sugar and but about 8% in the afiination syrup. .The term"aflination syrup includes the green aflination syrup and the washsyrup. 75 It is significant that the greater portion of the hydrogenperoxide initially introduced into the maish tank remains in theaflination syrup. Only that quantity of hydrogen peroxide is found-in'the damp washed sugar as is present in the liquor adhering to the sugarcrystals. This constitutes but an extremely small portion of thehydrogen peroxide and can in all cases be disregarded. Most of thehydrogen peroxide remains in the aflination syrup and a large portionthereof is returned to the maish tank with the wash syrup and aboutsix-sevenths of the green aflination syrup. .The approximatelyone-seventh of the green aflination syrup, which is diverted andpermitted to flow to the blow up tanks, contains a substantial quantityof hydrogen peroxide (about one-seventh of the amount present in themagma) which amount will subsequently be specified in connection withthe discussion as to the amounts of our active clarifying agent to usein the various phases of the process.

We will now direct our attention to the damp washed sugar. Water isadded to this sugar in order to prepare the washed sugar liquor, andthis water may either be pure water or the previously mentioned sweetwater. In commercial practice it is usual to use sweet water so thatlosses in power due to the necessity of concentrating the sweet watermay be avoided to as large an extent as possible. In practice it iscustomary to make up a melt of washed sugar liquor having a gravity ofabout Brix which means that it contains 60% sucrose. The Brix scale isbased upon the percentage of sucrose in the sugar liquor being tested.

The washed sugar liquor is then fed into drag tanks where it is treatedmechanically to remove impurities present therein such as scraps ofcane, refuse of various .sorts and pieces of bagging. But littleattention need be paid to these drag tanks which may be of variousforms. In one form a series of paddles on an endless conveyor is used toremove the foreign particles from the solution.

The washed sugar liquor is then fed to the blow up tanks. In these tanksmilk of lime is added and the mixture thoroughly intermixed by theagency of compressed air and live steam. An elevated temperature, one inthe neighborhood of 185 F. is utilized. Here the alkali treatment takesplace and many of the inorganic impurities usually termed ash areconverted to a state from which they may be removed by filtration.Although our process may sometimes operate without the blow up treatmentwith alkali we prefer to so operate, since this step also serves theimportant function of adjusting the pH of the sugar liquid to correspondwith that of substantial neutrality. If omitted, an alkali treatmentstep of some sort must be used in most cases in order to adjust the pHof the sugar liquor. During this step the pH of the solution may beraised as high as 9.0 since during the latter portions of the processthe pH may tend to drop somewhat.

From the blow up tanks the liquor is fed to a series of Sweetland filterpresses where it is filtered under a pressure in the neighborhood of 50pounds per square inch. In the process of filtration a cloudy filtrateis first obtained which is recycled as shown and sent through theSweetland presses another time. In these filter presses kieselguhr isordinarily added in order to render the filtering operation moreeflicient. A clear filtrate, which is optically clear but which stillcontains various discoloring compounds, is collected and subjected tofurther treatment. The pH throughout various other. Portions. of theprocess, and if tne plant is operating satisfactorily and the right;quantity in th Sweetland filters after the filtration are removed 1 and[subjected to various; treatments which need not here bedescribed, inorder that 10 the active materials may be reclaimed.

be speclfied'is now added to the clear liquor forms mg; thefiltrate. Incommercial operations the clear, liquoris usually pumpedto a ,relativelyhigh 15 portion of the refinery. where its temperature is sugarliquorduring this 20 accomplishes the decolorizing. It is' substantial liquorreaches the bone char filters substantially 1y completely decomposedduring this step. The elevated temperature is notnecessary for hy--drogen peroxide decomposition but is characteristic of the sugarrefining method used in large; 5 scale refineries. p After substantiallycomplete decomposition 'of hydrogen peroxide solution in the peroxidetreatment tank the solution is fed to the bone char filters. In"the bonechar filters the temperao ture at the start is usually about 145 F. butit rises to" 165 to 175 F. -during the filtration. This is due to anexothermic adsorption which oc-' ours. It is significant that at thetime the clear all the hydrogen, peroxide present 1 therein iscompletely decomposed. Ordinarily in the proc-' ess described, about 16minutes is required for the clear liquor to fiow from the collectingtank below the Sweetland presses tothe entry to thebonechar filters.This includes the time the liquor is in the conduits and in the peroxidereactiontank.

During't is period decomposition of the hydrogen peroxide slowly occurseffecting the decolorization and clarification of the sugar juices.Thisis .1 tobecontrasted with the rapid oxygen evolution processes ofthe prior art in which almost immediate decomposition of the hydrogenperoxide was obtained either through the agencyof catalysts for hydrogenperoxide decomposition suchas a bone charor by other methods. While atemperai tureof 165 F is maintained in theperoxide reaction vessel thistemperature is necessaryin order that the solution may have asufiiciently reduced viscosity to permit flow to the bone char filterand also to result in better adsorption of colored bodies. However, anexcessively high temperature is not necessary nor desirable in ourprocess. Since our process is to be applied to commercial operations,conditions under which the hydrogen peroxide solutions function todecolorize must, however, conform to thoseprevalent: in the commercialmethods. V t After passing through the bone char filters the solution istreated in variousways to recover the sugar in crystalline form. It maybe'noted that the bone char 'filtersmayialso be fed by thesugarcontainingliquor resulting from treatment of the aifination' syrup,whichltreatment will presently be described. The treatment to recoverthe sugar 0 in" crystalline form constitutes no part of our procesandwill not bedescribed i detail." Ordinarily it consists of variousconcentrating, evapo rating and centrifuging 1 steps. ,The sugar isusually obtained as'cr'ystals in vacuum pans. The

75 clarification and decolorization is complete after of milk of lime orother alkali 5 is being utilized it falls within the specifi'edrange;The lime and kleselguhr cakes present Hydrogenperoxide in amountssubsequently fto' valuable ingredients.

whiteness and are very satisfactorily decolorized.

We will now returnto the greenamnatlon syrnp'of which, it will beremembered, about one seventh is diverted after the centrifuging to blowup tanks. These tanks are similar to those described in connection'withthe treatment of the damp washed sugar. Here again milk of lime is addedto the green afiinatlon syrup and the mix-- ture thoroughly agitated bycompressed air and live steam. The quantity of milk of lime isdetermined in accordance with the kind of sugar being treated and theconcentration of the liquor, in order that the pH should not varysubstantially from that equivalent toneutrality. This means that thequantity used is sufiicient to bring the pH within the range 6.0 to 9.0.

From the blow up tanks the treated green affination'syrup fiows throughSweetland filter presses. Here the syrup is filtered free of thoseprecipitates resulting from treatment of the ashy substances with alkaliin the blow up tanks. It is customary in the Sweetlan'd filter presses,as de-. scribed in connection with the other phase of our process, tooperate with kieselguhr present as a filter aid. Ordinarily a pressureof about 50 pounds per square inch is usual in the Sweetland filterpresses. After completion of the filtration the solid material,consisting chiefly of kieselguhr," lime and various inorganicprecipitates, is removed and'treated in order to recover the Thistreatment forms no part of our processand need not be described indetail. v

" As in the othe portion-of the process the liquid first flowing throughthe Sweetland filter presses is acloudy solution and is returned forfurther filtration. The clear light liquor finally coming from thefilters has a sucrose content equivalent to'about 18 Brix. As shown,this is permitted to flow into multiple effect evaporators where it isconcentrated sufiiciently to increase its sucrose content to about 60Brix. This liquor termed clear dark liquor also fiows to the bonecharfilters and is treated simultaneously with or subsequently to the clearliquid obtained from the damp washed sugar phase of the process. Ofcourse, in manyrefineries employing many char filters. the filtersemployed for the afilnation syrup maybe different from those used intreating the washed sugar liquor.

ify" and 'decolorize thisgreen 'affination' syrup is more expensive thanclarifying the damp washed sugar since it involves theme of largeramounts of all chemicals. For economicaloperation it is,- orcourse,'essentia1'that'this 8% be recovered. It is significant thatwhile hydrogenperoxide solution is added-Ito. the clear liquor emergingfromthe Sweetland filter presses. in the damp washed sugar portion ofthe treatment, no hydrogen peroxide added during thecourse'of stepsconstituting treatment. 1 This" s because theafllnation syrup originallycontains sufiicient hydrogenperoxide while thedampwa'shed' sugarcontains only an inconsequential amount resulting from that present'inthe liquor which adheres to the crystals.

The green aflination syrup is obviously subthe green afiination .syrupdark liquor and collectsat the outflow end of the multiple eifectevaporators. This period of time amounts to about three hours in theprocess described thus illustrating the very slow character of ourprocess for treating the green afiination syrup with hydrogen peroxide.The hydrogen peroxide is slowly decomposed during this phase and is notrapidly decomposed as in the almost instantaneous oxygen evolutionprocesses of the prior art. The temperature never exceeds about 150F..during this portion of the process. The essential requirement in ourprocess for economical operation of the char filters is that the cleardark liquor be entirely free of undecomposed hydrogen peroxide at thetime it flows into the bone char filters. This is completely andentirely met by this described method of utilizing the hydrogenperoxide. Here again the use of elevated temperatures is avoided to asgreat an extent as consistent with commercial processes now in use. Theonly heating to which the greenaffination syrup is subjected is thatmoderate heating occurring in the blow up tanks and in the multipleeiiect evaporators.

The useof a temperature closely approximating the boiling point, such asis characteristic of prior methods, is to be avoided if at all possibleas undesirable in our decolorizing method.

a The amount of 100 volume hydrogen peroxide solution added to theaflination syrup (by introduction into the maish syrup or into someliquor so that it is carried to the maish syrup in the process) shouldvary from about 0.43 quart per 1000 lbs. of solid present in theaflination syrup treated to about 2.86; quarts per 1000 lbs. of solids.We have found that approximately- 1.43 quarts per 1000 lbs. of solidswill ordinarily yield the best results. Since a quart of 100 volumehydrogen peroxide weighs approximately 2.3 lbs. and has a hydrogenperoxide concentration of about 27.6%, these amounts may be specified inpounds of hydrogen peroxide per 1000 lbs. of solids treated. Thus theamount of hydrogen peroxide (H202) added in the solution of hydrogenperoxide should vary from 0.27 lb. per 1000 lbs. of 'solids'treated toabout 1.77 lbs. per 1000 lbs. of solids treated and should preferably beabout 0.89 lb. per 1000 lbs.'of solids. These values apply to theaflination syrup diverted to the blow up tanks and are based on theamount of affination syrup thus diverted. The hydrogen peroxide solutionis, however, as previously specified, added directly to the maish syruptanks.

With respect to the washed sugar liquor we v have found that the amountof 100 volume hydrogen peroxide solution present for each 1000 lbs. ofsolids in the washed sugar liquor being treated should vary from about0.12 quart to 0.30 quart. For best results we have ordinarily found thatabout 0.18 quart of 100 volume hydrogen peroxide solution per 1000 lbs.of solids in the washed sugar liquor being treated are desirable. Thesevalues may also be expressed in pounds of hydrogen peroxide per 1000lbs. of solids, in the washed sugar liquor being treated. Thus, amountsranging from 0.07 lb. to 0.19 lb. may be used, the best results beingobtained when 0.11 lb. of hydrogen peroxide are added in the hydrogenperoxide solu tion, these amounts being per 1000 lbs. of solids in thesugar liquor being treated.

The amount of H202 to be added in the hydrogen peroxide solution mayalso be expressed on the basis of percentage, the hydrogen peroxidepercentage being that amount of the peroxide present based on theweight. of the solids in the sugar liquor being treated. Thus, in theafllnatio'n syrup we have found amounts ranging from 0.027% to 0.177% ofhydrogen peroxide to be desirable, the best results being obtained withapproximately 0.089% present in the aflination syrup diverted to theblow up tanks. We have found the percentage ofhydrogen peroxidenecessary in the washed sugar liquor to be somewhat less, ranging from0.007% to 0.019%, the best results being obtained when there isapproximately 0.011% hydrogen peroxide present. It is obvious that formostsugars the percentage of hydrogen peroxide necessary may be givenwith sufiicient accuracy as about 0.09% in the green amnation syrup andabout 0.01% in the washed sugar liq uor. Obviously about nine times asmuch hydrogen peroxide is necessary in the green atfination syrup stageand this is primarily due to the fact that this liquor contains a muchlarger amount of dark colored impurities. These amounts are based on thequantity of solids in the aflination syrup diverted to the blow up tanksand on the amount of solids'in the washed sugar liquor fed to theperoxide reaction vessel.

Furthermore, we have found that the use 01' hydrogen peroxide under theconditions disclosed as characteristic of our improved process destroysto a. very high degree those bacteria and ferments which are ordinarilypresent in sugar liquors and which are objectionable in the finishedproduct whether it be in the completely refined crystalline sugar or inthe refiners syrup. These bacteria and ferments 'are those producing asulfurous odor and those termed fiat sours in the sugar industry. Whenpresent in refined sugar or refiners syrup those of the first class tendto develop sulfur containing gases, particularly hydrogen sulfide, uponstanding. This is particularly objectionable when the sugar is used incanning since-the development of gases in an' en-' closed space.causes'bulging and breakage of the cans. The fiat sours causedecomposition of the food product and the development of acidity. Ourmethod completely eliminates these dangers, because it destroys theseobjectionable organisms.

It is to be understood that the various procedures herein disclosed areto be considered as illustrative and not restrictive. Various changesmight be made in the precise steps herein outlined without departingfrom the spirit of ourinvention. The refining process outlined in theflow sheet is but a typical one and many changes might be made thereinwhichwould fairly come within the scope of our invention.

We claim:

1. A process for decolorizing a liquor containing cane sugar whichcomprises the steps of rendering said liquor substantially neutral inreaction by subjecting said liquor to the action of an alkali at atemperature in excess of room temperature but below the boiling point ofsaid sugar containing liquor, subjecting said liquor to the action ofhydrogen peroxide under conditions such that rapid decomposition of thehydrogen peroxide is substantially completely avoided, added catalystsfor the decomposition of hydrogen peroxide being substantially absentduring said treatment, permitting said liquor to stand until thehydrogen peroxide therein has been substantially completely decomposed,and subsequently passing said liquor through an adsorbent filter, said75 sugar-containing liquidWbeing maintained sub stantiailyneutra'laduring the entire process. J 2. A processdordecolorizingialiquori containing cane sugar which comprises the steps ofrenderingsaid liquor sub'stantially neutral in reaction by subjectingit-to the action of milk of 'oxide therein is substantially completelydecomposed, and subsequently passing said sugar-containing liquorthrough a bone char filter, said liquor being maintained substantiallyneutral in reaction throughout the entire process.

3. A process for decolorizing a liquor containing cane sugar whichcomprises the steps of treating said liquor with lime at a temperaturein the neighborhood of '185" F. in order to render it substantiallyneutral in reaction, and subjecting 5 said substantially neutral liquorto the action or hydrogen peroxide under conditions such that rapiddecomposition of said hydrogen peroxide is avoided, added catalysts forthe decomposition canesugarw" 1 6.:A-method o1: refining raw cane sugarwhich comprises the steps ofadmixing; an aqueous liquid "containinghydrogen peroxide, with said raw sugar in orderto form a magma,subjecting said magma to centrifugation in order to separate crystals ofdamp washed sugar from the remaining aflination syrup, adding water tosaid damp washed sugar crystals in order to prepare a sugar containingliquor, subjecting said sugar containing liquor to the action of analkali at a temperature in excess of-room temperature but below theboiling point of said sugar containing liquor in order to render saidliquor substantially neutral in reaction, filtering, adding hydrogenperoxide to said substantially neutral filtrate,

\ added catalysts for the decomposition of hydrogen peroxide beingsubstantially absent from said sugar-containing liquor, permitting saidtreated liquor to stand until the hydrogen peroxide therein issubstantially completely decomposed, subjecting said neutral filtrate tothe-action of an adsorbent agent in order to complete the deof hydrogenperoxide being substantially absent 0 during said treatment.

4. A method of decolorizing a liquor containing cane sugar whichcomprises the steps of subjecting said liquor to the action of hydrogenperoxide under conditions such that rapid decomposition of said hydrogenperoxide is substantially completely avoided, added catalysts for thedecomposition of hydrogen peroxide being substantially absent duringsaid treatment, and then subjecting said liquor to the action of anadsorbent decolorizing medium, said liquor being substantially free ofundecomposed hydrogen peroxide during said latter step and also beingsubstantially neutral in reaction throughout the entire process.

5. A method of refining raw cane sugar which comprises the steps ofadmixing an aqueous liquid containing hydrogen peroxide with said rawsugar in order to form a magma, subjecting said magma to centrifugationin order to separate crystals of damp washed sugar from the remainingaifination syrup, adding water to said damp washed sugar crystals inorder to prepare a sugar-containing liquor, subjecting saidsugarcontaining liquor to the action of milk of lime in order to renderit substantially neutral in reaction, filtering and adding hydrogenperoxide to said substantially neutral filtrate, added catalysts for thedecomposition of hydrogen peroxide being substantially absent from saidsugar-containing liquor, permitting said filtrate to stand until saidhydrogen peroxide therein is substantially completely decomposed,passing said filtrate through a bone char filter in order to completethe clarification and decolorizing, subjecting a portion of saidafiination syrup to the action of milk of lime in order to render itsubstantially neutral in reaction, filtering said limed aflination syrupin order to obtain a clear filtrate, concentrating said filtrate, saidconcentrated filtrate being substantially free of undecomposed hydrogenperoxide, passing said concentrated filtrate through a bone char filterin order to complete the clarification and decoloriza- 5 tion, andtreating said sugar-containing liquids colorization, and subsequentlytreating said filtrate in order to recover refined crystalline canesugar.

'7. A method of refining raw cane sugar which comprises the steps ofadmixing an aqueous liquid containing hydrogen peroxide with said rawsugar in order to form a magma, added catalysts for the decomposition ofhydrogen peroxide being substantially absent both from said aqueousliquid and said raw sugar, subjecting said magma to centrifugation inorder to separate the crystals of damp washed sugar from the remainingaflination syrup which contains the major portion of the added hydrogenperoxide, returning a portion of said afiination syrup to said aqueousliquid which is admixed with the raw cane sugar to form said magma,subjecting the remaining portion of said aflination syrup to the actionof an alkali at a temperature in excess of room temperature but belowthe boiling point of said sugar containing liquor in order to render itsubstantially neutral in reaction, filtering, concentrating saidsubstantially neutral filtrate, said concentrated filtrate beingsubstantially free from hydrogen peroxide, subjecting said concentratedfiltrate to the action of an adsorbent agent in order to complete thedecolorization, and subsequently treating said filtrate in order torecover refined crystalline cane sugar.

8. In a process of refining raw cane sugar the steps which comprisepreparing a magma by the addition of an aqueous liquid to said raw canesugar, separating said magma into solid sugar crystals and afilnationsyrup, rendering said affination syrup substantially neutral inreaction, and subjecting said afiination syrup to the action of hydrogenperoxide in the absence of added catalysts for the decomposition ofhydrogen peroxide and under conditions such that rapid decomposition ofsaid hydrogen peroxide is substantially completely avoided in order todeseparately in order tc recover refinedcrystalline adjusting the pH ofsaid liquor until said solution is substantially neutral in reaction,subiecting said sugar-containing liquor to the action of hydrogenperoxide in the absence of added catalysts for the decomposition ofhydrogen peroxide and under conditions such that rapid decompositionthereof is substantially completely avoided and permitting saidsugar-containing liquor to stand until said hydrogen peroxide issubstantially completely decomposed, the liquor being decolorized duringthe standing process.

JOSEPH S. REICHERT. RALPH B. ELLIOTT.

